Thread: To get our part-MC a companion...?

Hello. I have a black fluffy cat called Angus.
He's only a quarter MC but has nearly all the main physical characteristics.
He's one and a half.
We adopted him six months ago. He's now settled and loves going outside. We both work FT but he seems to sleep a lot when we're our and keeps himself busy.
He's been a lot calmer since he had access outside whenever he wants, and since we feed him just once a day (he knows when it's coming rather than nagging for a second feed of the day!).
My girlfriend has raised the idea of another cat to keep him company and that that might help him deal with children a bit better in the future...
I'm a bit worried another cat will upset him just as he's finally settled with us.
He's very shy and as a kitten we think he was left alone at his former owners' house during the day. Being moved from home and new owners must be traumatic too.
He's now fine with us (it's still a struggle to brush him though!) and most adults. He just doesn't like my girlfriend's sister who, being a 'cat lady' with lots of Siamese was too forward and went straight to him and picked him up when he was quite new with us. He hasn't forgotten...!
He's settled in a routine now but quite guarded - often checks around his cat flap and keeps his distance from strangers and other cats.
He goes outside a lot but us very lazy inside. His wait shot up to 5.5kg do we had to lower his good to 40g dry and half a wet pouch a day. Now his weight is slowly coming down and he's never squeezing for food either.
I've read about how it's best to gradually introduce new cats to each other, and that it's best to get another cat of a similar build and age - we'd go for a female.
But what do people on here think? Would it be worth a shot for the long-term, or not worth the risk of upsetting him and really stressing him out.
Has anyone on here had a MC with similar character traits etc
Any advice would be appreciated.
Thanks very much.